Building better and safer isn’t a slogan, but the way we show up in the world.
It’s how we make sure technology speaks not only in code, but with meaning: better technologies, better ways of working, and more inclusive communities. We align with what matters for people and for the planet, actively nurturing it to be better and safer. At the center, it’s our people who power everything we do. It’s their talent, drive and different ways of thinking that keep us moving forward, pushing the limits of what’s possible.
The Role
We are looking for a driven engineer to join our growing railway systems team. You’ll be at the heart of delivering mission-critical software for train control systems — working to the highest safety standards (SIL2) and directly shaping how millions of passengers travel safely every day.
What you will do
- Design, develop, and validate PLC-based software for safety-critical railway applications, following EN 50657 standards up to SIL2.
- Apply your railway domain knowledge across the full lifecycle of the train control systems — from requirements through to integration.
- Collaborate with cross-functional teams (Systems, V&V, Safety) to ensure software quality and traceability throughout development.
- Produce and review technical documentation including Software Design Specifications, Software Architecture Specifications, and safety cases to SIL2 requirements.
Who You Are
- Minimum 2 years of experience in the railway domain, specifically in Train Control and Management Systems.
- Hands-on PLC programming experience.
- Proven track record delivering software up to SIL2 (EN 50657 or equivalent).
- You take ownership — you don't wait to be told there's a problem; you raise it and help solve it.
- Continuously improve your craft — staying current with railway standards, tooling, and best practices, and sharing knowledge across the team.
- Strong written and verbal communication in English; French is a nice to have.
What We Offer
Critical Software is a company built on technical excellence, trust, and genuine care for the work we do. As a Software Engineer, you will:
- Work on technology that matters — your code will be part of systems where safety is non-negotiable, directly impacting the reliability of rail networks in operation.
- Join a team with depth — collaborate with experienced engineers across Systems, V&V, and Safety.
- Grow your career — with access to continuous learning, internal mobility, and the support of a team that invests in your development.
- Work flexibly — across our offices in Lisbon, Porto, Coimbra, or Viseu, with a hybrid working model.
- Recharge when you need it — Sabbatical programme.
We also offer a competitive compensation package, health insurance, and the chance to do meaningful work alongside engineers who genuinely care about what they build.
Every day we embrace new missions across industries as diverse as aerospace, space, defense, transport, telecoms, government, energy, finance and healthcare. Now, the real question is: are you ready to join us and help make the world a better and safer place?
Critical Software is proud to be a Benefit Corporation. A Benefit Corporation differs from a standard corporation (C-Corporation): It is a for-profit business entity, legally defined in the US and other jurisdictions, whose legally defined goals include the positive impact on society, workers, the community and the environment, in addition to profit.
We are an equal opportunity workplace and committed to allow candidates with disabilities or neurodevelopmental conditions to prove their competencies to their full potential. We are willing to move the barriers that may prevent you from demonstrating that you are the right candidate for this role, so please let us know if you need some adjustment in your recruitment process.
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Skills Required
- Minimum 2 years of experience in the railway domain
- Hands-on PLC programming experience
- Proven track record delivering software up to SIL2
What We Do
At Critical Software, we believe our people are the core of who we are. Their talent, diversity, and ability to go beyond expectations shape everything we do. Working at Critical is about being part of a community built on purpose, values, and collaboration. Our commitment to engineering excellence makes us a trusted partner for some of the world’s leading companies in Aerospace, Railway, Medical Systems, Energy, Finance, and many more. We believe that technology is nothing without a passion to use it for good. That’s why we engineer change, helping to build a better and safer world through trusted and transformative technologies. Since 1998, we’ve helped companies in global industries like aerospace, transport, energy, healthcare and finance. Across the world, people and organisations depend on what we do. And we like that. Because it means that technology isn’t just our business. It’s our chance to help change the world. More than a company, we are a community. Our togetherness, culture and values are the foundations of who we are and what we do. We are proud to hold Benefit Corporation status, reflecting our commitment to sustainability, transparency, and business for good. We’re also one of only a few tech companies in the world to have both our waterfall and agile software development processes rated at CMMI® Level 5. Just as important as our technical expertise is our strong company culture, which guides us in everything we do. We’re recruiting for all of our locations right now and, if you’d like to find out more, please take a look at the careers section of our website.
